Monitor has lost signal

Hi, wondering if anyone can help me.

About 4 months ago my desktop monitor got the message "no signal". After much searching,checking and trying many things I finally connected the monitor directly to the computer instead of through the video card and it worked. So put it down to the video card packing it in.

A few days ago it decided to not receive a signal again. My son was watching tv show on the system and apparently it froze. He tried to reboot the system and then there was no signal to the monitor.

I have taken out the bios battery, even replaced it now, have taken out the ram and tested one at a time and still no signal. The monitor is working as I have attached it to my laptop and all was fine.

The computer appears to be booting but I am not getting the start up beep anymore.

Any ideas:confused:

Thanks